Such transducers are already known.
One known electret transducer is equipped with a diaphragm electrode and a flat, counter polarity carrying, perforated backplate. The latter forms on the side, facing the diaphragm, precisely placed supporting protrusions on which the diaphragm rests and is mounted on its circumference.
An electret transducer is disclosed in Murphy U.S. Pat. No. Re. 28,420, "Electret Acoustic Transducer", issued May 13, 1975.
In Griese German Pat. No. 2,200,150, granted Jan. 13, 1977, an acoustic chamber diminishing in height as it becomes more remote from a side-entering sound signal is disclosed.